Stdlib: DOMImplementation::createDocument() optional args — 2-arg form fatal (ext/dom/php_dom.c) #14408

Summary

DOMImplementation::createDocument(?string $namespace = null, string $qualifiedName = \"\", ?DOMDocumentType $doctype = null) accepts 0–3 arguments in php-src. VM requires exactly 3 user arguments and throws LogicException: expects exactly 3 arguments for the common 2-arg createDocument(null, 'root') form Zend accepts.

Blocks factory code that creates empty or named-root documents without an explicit doctype.

php-src reference

• ext/dom/php_dom.c — dom_implementation_create_document
• ext/dom/dom.stub.php — DOMImplementation::createDocument
• Current VM: ext/dom/ImplementationCreateDocument.php — arity check count($frame->calledArgs) < 4

PHP implementation target

• ext/dom/ImplementationCreateDocument.php — default $qualifiedName to '' and $doctype to null when omitted; match Zend arity/TypeError messages

Repro (php-src-strict)

./script/docker-exec.sh -- php test/repro/maintainer_gap_dom_implementation_create_document_optional.php          # Zend: ok
./script/docker-exec.sh -- php bin/vm.php test/repro/maintainer_gap_dom_implementation_create_document_optional.php  # VM: LogicException arity

Done when

• 0–3 argument forms match php-src signatures and behavior (php-src-strict)
• test/repro/maintainer_gap_dom_implementation_create_document_optional.php green on VM
• PHPUnit guard; VM/JIT/AOT agree when both in scope